There is a need to crease, i.e. more sharply define the folded edges of paper produces, particularly bundles of folded printed products such as e.g. newspapers or magazines, in order to reduce the thickness difference between the area of the folded edge and the areas of the other edges which are not folded and therefore produce products, which are easier to further process and from which it is e.g. possible to more easily produce stable stocks or layers. According to the prior art the folded printed products, e.g. arriving in the form of a scale flow from a rotary press are passed for the purpose of pressing the usually leading folded edge between one or more pressing roller pairs positioned transversely to the scale flow movement direction and the two rollers of a pair are pressed against one another with a pressing force and the folded edges are very briefly, and intensely pressed. It has been found that even when using very high pressing forces (e.g. approximately 100 to 200 kp) when using such pressing roller pairs folded edges are obtained, which in part "relax" again, i.e. still give rise to a considerable thickness difference between the area of the pressed folded edge and the other areas of the printed product. It is obvious to use the fold pressing method with transverse pressing roller pairs in the case of printed products in a scale flow formation, so that the rollers are normally positioned immediately in the rotary press discharge area, where the printed products are still very fresh. Therefore significantly higher pressing forces cannot be used for pressing the folded edges, because the quality of the printed products would be deteriorated by the sticking or smearing of the inner pages.
Other methods are known in which the folded edges are briefly pressed with high pressing forces and which in all cases only lead to edges having a limited sharpness and which are therefore only usable to a limited extent.
In order to obviate these disadvantages, as described in European patent 207271 of the same applicant, a method has been developed according to which the folded edge of folded printed products is pressed between two pressing jaws for a longer period. To enable this method to be used on continuously conveyed products, the pressing jaw pairs move over a distance with the printed products conveyed in suspended manner. It has been found that also in the case of this method a folding quality meeting higher demands can only be achieved with very high pressing forces.